MySQL主主同步跟MySQL主从同步类似，只是再另一台上反向再做一次主从同步。
只不过MySQL的配置文件有些地方需要注意一下。
实验环境
| 名称 | IP地址 | 系统版本 | MySQL版本 |
|---|---|---|---|
| testA | 192.168.1.235 | CentOS 6.5 | mysql-5.7.13 |
| testB | 192.168.1.237 | CentOS 6.5 | mysql-5.7.13 |
1. 创建用于同步数据的用户
a. testA服务器
grant replication slave on *.* to 'sync'@'192.168.1.237' identified by '<YourPassword>'; #IP地址可以指定固定的IP，提高安全性。若用'%'则表示所有的IP均可
flush privileges;
b. testB服务器
grant replication slave on *.* to 'sync'@'192.168.1.235' identified by '<YourPassword>'; #IP地址可以指定固定的IP，提高安全性。若用'%'则表示所有的IP均可
flush privileges;
2. MySQL数据库配置文件的注意点
[mysqld]
server-id = 1 #[必须]服务器唯一ID，每台服务器需不同
log-bin = /home/mysql/mysql-bin #[必须]启用二进制文件
binlog_format = mixed #[不是必须]二进制文件启用混合模式
expire-logs-days = 14 #[不是必须]二进制文件过期时间，单位是天
sync-binlog = 1 #[不是必须]当每进行1次事务提交之后，MySQL将进行一次磁盘同步指令来将binlog_cache中的数据强制写入磁盘
# MASTER DB #
binlog-do-db = test,androidpnserver #[不是必须]只将对应的数据库变动写入二进制文件。如果有多个数据库可用逗号分隔,或者使用多个binlog-do-db选项
binlog-ignore-db = mysql,information_schema,performance_schema #[必须]不需要记录二进制日志的数据库。如果有多个数据库可用逗号分隔，或者使用多个binlog-do-db选项。一般为了保证主主同步不冲突，会忽略mysql数据库。
auto-increment-increment = 10 #[必须]
auto-increment-offset = 1 #[必须]
#做主主备份的时候，因为每台数据库服务器都可能在同一个表中插入数据，如果表有一个自动增长的主键，那么就会在多服务器上出现主键冲突。
#解决这个问题的办法就是让每个数据库的自增主键不连续。上面两项说的是，假设需要将来可能需要10台服务器做备份，将auto-increment-increment设为10。而auto-increment-offset=1表示这台服务器的序号。从1开始，不超过auto-increment-increment。
# SLAVE DB #
replicate-do-db = test,androidpnserver #[不是必须]只同步对应的数据库。如果有多个数据库可用逗号分隔，或者使用多个replicate-do-db选项
replicate-ignore-db = mysql,information_schema,performance_schema #[必须]不需要同步的数据库。如果有多个数据库可用逗号分隔，或者使用多个replicate-ignore-db选项。一般为了保证主主同步不冲突，会不同步mysql数据库。
relay_log = /home/mysql/relay-bin #[不是必须]开启中继日志，复制线程先把远程的变化复制到中继日志中，再执行。
log-slave-updates = ON #[必须]中继日志执行之后将变化写入自己的二进制文件
slave-skip-errors = all #[不是必须]跳过所有的sql语句失败
a. testA的数据库配置文件
# For advice on how to change settings please see
# http://dev.mysql.com/doc/refman/5.7/en/server-configuration-defaults.html
# Configuration name server
[mysql]
# CLIENT #
port = 3306
default-character-set = utf8
[client]
socket = /home/mysql/mysql.sock
[mysqld]
#
# Remove leading # and set to the amount of RAM for the most important data
# cache in MySQL. Start at 70% of total RAM for dedicated server, else 10%.
# innodb_buffer_pool_size = 128M
#
# Remove leading # to turn on a very important data integrity option: logging
# changes to the binary log between backups.
# log_bin
#
# Remove leading # to set options mainly useful for reporting servers.
# The server defaults are faster for transactions and fast SELECTs.
# Adjust sizes as needed, experiment to find the optimal values.
# join_buffer_size = 128M
# sort_buffer_size = 2M
# read_rnd_buffer_size = 2M
[mysqld]
# GENERAL #
user = mysql
default-storage-engine = InnoDB
socket = /home/mysql/mysql.sock
pid-file = /home/mysql/mysql.pid
character-set-server = utf8
lower-case-table-names = 1
performance_schema = ON
sql_mode = ''
server-id = 1
# MyISAM #
key-buffer-size = 32M
myisam_recover_options = FORCE,BACKUP
# SAFETY #
max-allowed-packet = 16M
max-connect-errors = 1000000
# DATA STORAGE #
datadir = /home/mysql/
# BINARY LOGGING #
log-bin = /home/mysql/mysql-bin
binlog_format = mixed
expire-logs-days = 14
sync-binlog = 1
log-bin-trust-function-creators= 1
# MASTER DB #
#binlog-do-db = mdm,androidpnserver
binlog-ignore-db = mysql,information_schema,performance_schema
auto-increment-increment = 2
auto-increment-offset = 1
# SLAVE DB #
#replicate-do-db = mdm,androidpnserver
replicate-ignore-db = mysql,information_schema,performance_schema
relay_log = /home/mysql/relay-bin
log-slave-updates = ON
# CACHES AND LIMITS #
tmp-table-size = 32M
max-heap-table-size = 32M
query-cache-type = 0
query-cache-size = 0
max-connections = 500
thread-cache-size = 50
open-files-limit = 65535
table-definition-cache = 1024
table-open-cache = 2048
# INNODB #
innodb-flush-method = O_DIRECT
innodb-log-files-in-group = 2
innodb-log-file-size = 256M
innodb-flush-log-at-trx-commit = 1
innodb-file-per-table = 1
innodb-buffer-pool-size = 4G
# LOGGING #
log-error = /home/mysql/mysql-error.log
log-queries-not-using-indexes = 1
#slow-query-log = 1
#slow-query-log-file = /home/mysql/mysql-slow.log
# Disabling symbolic-links is recommended to prevent assorted security risks
symbolic-links=0
b. testB的数据库配置文件
# For advice on how to change settings please see
# http://dev.mysql.com/doc/refman/5.7/en/server-configuration-defaults.html
# Configuration name server
[mysql]
# CLIENT #
port = 3306
default-character-set = utf8
[client]
socket = /home/mysql/mysql.sock
[mysqld]
#
# Remove leading # and set to the amount of RAM for the most important data
# cache in MySQL. Start at 70% of total RAM for dedicated server, else 10%.
# innodb_buffer_pool_size = 128M
#
# Remove leading # to turn on a very important data integrity option: logging
# changes to the binary log between backups.
# log_bin
#
# Remove leading # to set options mainly useful for reporting servers.
# The server defaults are faster for transactions and fast SELECTs.
# Adjust sizes as needed, experiment to find the optimal values.
# join_buffer_size = 128M
# sort_buffer_size = 2M
# read_rnd_buffer_size = 2M
[mysqld]
# GENERAL #
user = mysql
default-storage-engine = InnoDB
socket = /home/mysql/mysql.sock
pid-file = /home/mysql/mysql.pid
character-set-server = utf8
lower-case-table-names = 1
performance_schema = ON
sql_mode = ''
server-id = 2
# MyISAM #
key-buffer-size = 32M
myisam_recover_options = FORCE,BACKUP
# SAFETY #
max-allowed-packet = 16M
max-connect-errors = 1000000
# DATA STORAGE #
datadir = /home/mysql/
# BINARY LOGGING #
log-bin = /home/mysql/mysql-bin
binlog_format = mixed
expire-logs-days = 14
sync-binlog = 1
log-bin-trust-function-creators= 1
# MASTER DB #
#binlog-do-db = mdm,androidpnserver
binlog-ignore-db = mysql,information_schema,performance_schema
auto-increment-increment = 2
auto-increment-offset = 2
# SLAVE DB #
#replicate-do-db = mdm,androidpnserver
replicate-ignore-db = mysql,information_schema,performance_schema
relay_log = /home/mysql/relay-bin
log-slave-updates = ON
# CACHES AND LIMITS #
tmp-table-size = 32M
max-heap-table-size = 32M
query-cache-type = 0
query-cache-size = 0
max-connections = 500
thread-cache-size = 50
open-files-limit = 65535
table-definition-cache = 1024
table-open-cache = 2048
# INNODB #
innodb-flush-method = O_DIRECT
innodb-log-files-in-group = 2
innodb-log-file-size = 256M
innodb-flush-log-at-trx-commit = 1
innodb-file-per-table = 1
innodb-buffer-pool-size = 4G
# LOGGING #
log-error = /home/mysql/mysql-error.log
log-queries-not-using-indexes = 1
#slow-query-log = 1
#slow-query-log-file = /home/mysql/mysql-slow.log
# Disabling symbolic-links is recommended to prevent assorted security risks
symbolic-links=0
3. 分别重启MySQL服务
service mysqld restart
4. 查看主服务器状态
a. testA服务器
mysql> flush tables with read lock; #防止进入新的数据
Query OK, 0 rows affected (0.00 sec)
mysql> show master status\G;
*************************** 1. row ***************************
File: mysql-bin.000010
Position: 64353552
Binlog_Do_DB:
Binlog_Ignore_DB: mysql,information_schema,performance_schema
Executed_Gtid_Set:
1 row in set (0.00 sec)
b. testB服务器
mysql> flush tables with read lock; #防止进入新的数据
Query OK, 0 rows affected (0.00 sec)
mysql> show master status\G;
*************************** 1. row ***************************
File: mysql-bin.000008
Position: 64355767
Binlog_Do_DB:
Binlog_Ignore_DB: mysql,information_schema,performance_schema
Executed_Gtid_Set:
1 row in set (0.00 sec)
5. 使用change master语句指定同步位置
a. testA服务器
CHANGE MASTER TO MASTER_HOST='192.168.1.237',MASTER_USER='sync',MASTER_PASSWORD='<YourPassword>',MASTER_LOG_FILE='mysql-bin.000008',MASTER_LOG_POS=64355767;
b. testB服务器
CHANGE MASTER TO MASTER_HOST='192.168.1.235',MASTER_USER='sync',MASTER_PASSWORD='<YourPassword>',MASTER_LOG_FILE='mysql-bin.000010',MASTER_LOG_POS=64353552;
6. 分别启动从服务器线程
mysql> start slave;
Query OK, 0 rows affected (0.00 sec)
7. 查看从服务器状态
a. testA服务器
mysql> show slave status\G;
*************************** 1. row ***************************
主要关注以下 2 个参数：
...
...
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
...
...
b. testB服务器
mysql> show slave status\G;
*************************** 1. row ***************************
主要关注以下 2 个参数：
...
...
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
...
...
8. 验证测试
略
